session UTM = HOL +
  options [document = false]
  theories
    "thys/Turing"
    "thys/Turing_Hoare"
    "thys/Uncomputable"
    "thys/Abacus_Mopup"
    "thys/Abacus"
    "thys/Abacus_Defs"
    "thys/Rec_Def"
    "thys/Recursive"
    "thys/UF"
    "thys/UTM"
session ITP in Paper = UTM +
  options [document = pdf, document_output = "..", document_variants = "paper"]
  theories
    "Paper"
session Slides1 in Slides = UTM +
  options [document = pdf, document_output = "..", document_variants = "slides1"]
  theories
    "Slides1"
session Slides2 in Slides = UTM +
  options [document = pdf, document_output = "..", document_variants = "slides2"]
  theories
    "Slides2"